Speaking of rock band debut albums that sound nothing like what they eventually became popular for: Let’s talk about the first Journey album!
Journey first formed as an instrumental prog rock / jazz fusion band with ex-members of Santana’s backing band (Neal Schon of course plus Gregg Rolle on vocals(!) before he got downgraded to just the keyboardist once Steve Perry arrived for “Infinity”).
The band also originally included Aynsley Dunbar on drums, fresh from his stint in Frank Zappa’s Mothers. Like I mentioned, the first album is mostly prog rock based, and doesn’t really reach for pop hits like the Steve Perry-fronted group ended up doing.
The first song “Of A Lifetime” is a 7 minute epic that sets the tone right out of the gate. There’s even two instrumentals (“Kohoutek” and “Topaz”) that veer into Pink Floyd-esque space rock.
In fact, they recorded a few more instrumentals in this vein that weren’t included on the album (worth seeking out).
Overall a pretty solid overlooked catalog album.